1. Field of the Invention
The invention relates to apparatus for cooling a work roll in a rolling mill for rolling metal strip. Such apparatus has sprays arranged in a row extending in the longitudinal direction of the work roll, which sprays are directed at the surface of the work roll and spray cooling water onto the work roll surface during cooling of the work roll.
The invention will be described in this specification especially in connection with the hot strip rolling of steel; however, the invention may also be used in the cold rolling of steel, and in the rolling of metals other than steel.
2. DESCRIPTION OF THE PRIOR ART
In hot strip rolling, the work rolls, i.e. the rolls which come directly into contact with the rolled material, become hot. The temperature of these work rolls must not become too high, however, because the increased temperature causes thermal deformation of the work rolls, thereby rendering the strip profile, i.e. the variation of thickness of the strip in the direction perpendicular to the strip length, unacceptab1e. Moreover, high temperature of the work rolls leads to rapid wear of the work roll. For these reasons, it is normal for the work rolls to be cooled by spraying apparatus.
U.S. Pat. No. 2,921,488 shows cooling sprays in single rows on each side of the roll, in which thin spray jets have their axes inclined to the roll surface and have contact lines on the roll surface which are very slightly inclined (at 4.degree.) to the longitudinal axis of the roll, so that they substantially form a continuous line parallel to the roll axis. The aim is to direct and hold the cooling water in the roughly V-shaped zone adjacent the contact line of two adjacent rolls.
SU-A No. 471912 shows a row of sprays on each side of the roll. The contact surfaces of the spray jets are oblong and all inclined at 30.degree. to the axis of the roll. Over most of the roll length, each adjacent pair of contact surfaces are mutually offset in the circumferential direction of the roll. The aim in this disclosure is more uniform cooling and use of less cooling water.
SU-A No. 995933 (see "Soviet Inventions Illustrated", Derwent Publications Ltd. No. 83-832211/48 M21 P51) shows a single row of sprays of which each contact area is at 70.degree.-75.degree. to the roll axis. To achieve sectional control of the thermal profile of the roll, the contact areas are oppositely inclined to the roll axis on the two sides of the central radial plane of the roll.
Arranging oblong contact surfaces of the jets at an angle to the axis, e.g. 30.degree. as mentioned above, has been found of benefit.
One problem that can arise in cooling work rolls using apparatus known in practice, in the case of hot strip rolling and particularly at a high production rate, is that the work rolls cannot be cooled sufficiently, with the result that extra waiting time must be allowed between the rolling of two consecutive hot strips.